High-speed non-impact laser printing apparatus

ABSTRACT

A printing apparatus for laser recording of data in which a complete row of characters is simultaneously formed by a two dimensional matrix of parallel diode lasers selectively activated to emit light in character shapes upon a photosensitive medium. The invention is adapted to provide rapid non-impact printout, in alphanumeric characters, of computer data. The system simultaneously imprints a complete row of characters on a medium transported through the system at high speed, and for each character in the row the system includes a decoder for converting data in computer binary code into individual signals each representing a single alphanumeric character. The individual signals are applied through a hardwiring distribution circuit or core distribution circuit to selected diode lasers in the two dimensional matrix to cause those lasers to emit parallel beams of light in a pattern approximating the shape of the character. The emitted light beams directly strike a photosensitive medium, causing it to record the character shape. Spacing between rows of characters is controlled by a timing signal supplied by the means transporting the photosensitive medium through the system.

United States Patent [191 Mee [451 Sept. 17, 1974 HIGH-SPEED NON-IMPACTLASER PRINTING APPARATUS [76] Inventor: John L. Mee, 42 Highwood Rd.,

Farmington, Conn. 06032 [22] Filed: Apr..l6, 1973 [21] Appl. No.:351,620

[52] US. Cl. 354/5, 354/7 [51] Int. Cl B4lb 21/14 [58] Field of Search95/45; 340/378, 324; 354/5, 7

[56] References Cited UNITED STATES PATENTS 3,267,455 8/1966 McGuire340/324 3,611,891 10/1971 McNaney 95/45 Primary Examiner-John M. HoranAttorney, Agent, or Firm-Joseph L. Lazaroff [57] ABSTRACT A printingapparatus for laser recording of data in IIOOOOII 2 which a complete rowof characters is simultaneously formed by a two dimensional matrix ofparallel diode lasers selectively activated to emit light in charactershapes upon a photosensitive medium. The invention is adapted to providerapid non-impact printout, in alphanumeric characters, of computer data.The system simultaneously imprints a complete row of characters on amedium transported through the system at high speed, and for eachcharacter in the row the system includes a decoder for converting datain computer binary code into individual signals each representing asingle alphanumeric character. The individual signals are appliedthrough a hardwiring distribution circuit or core distribution circuitto selected diode lasers in the two dimensional matrix to cause thoselasers to emit parallel beams of light in a pattern approximating theshape of the character. The emitted light beams directly strike aphotosensitive medium, causing it to record the character shape. Spacingbetween rows of characters is controlled by a timing signal supplied bythe means transporting the photosensitive medium v through the system.

14 Claims, 12 Drawing Figures Pmmms'tnmu 3.838-,91T

T ms or 7 J COMPUTER FIGURE 2 j- TRANS.

3 INTERFACE I Anmw I 3.836.917 SHEET-50F 7 F-IIGUREI 4 4 3 TERMINAL 4 ITERMINAL LJZIY Pmmmsm m V sIHEU 70$ 7- FIGURE e COMPUTER HIGH-SPEEDNON-IMPACT LASER PRINTING APPARATUS BACKGROUND OF THE INVENTION 1. Fieldof the Invention The field of the present invention relates to printingand the graphic arts, and more particularly to high speed, non-impactprinters suitable for performing computer data printout tasks.

2. Description of the Prior Art The rate at which a computer can supplyoutput data far outstrips the ability of conventional mechanicalprinters to record that data. Accordingly, many attempts have been madeto find substitutes for mechanical printers to attain high printingspeeds and thus more efficient computer use.

Various arrangements have been proposed for high speed non-impactprinting using a photosensitive medium and optical character generationtechniques with laser light sources. In one such arrangement, disclosedin US. Pat. Nos. 3,396,401; 3,506,779; 3,654,864; and 3,656,] 75, alaser light source, providing either a point or line of light, scans therecording medium in a series of parallel lines, with switching meanscontrolling emission to generate character shapes.

In another prior art arrangement, disclosed in U'.S. Pat. No. 3,220,013,a laser light source is deflected through a character mask, and isthendeflected to-a common point, from which it is deflected to the recordingmedium.

In still another prior art arrangement, disclosed in US. Pat. Nos.3,4l0,203; 3,617,702; 3,653,067; 3,688,281; and 3,704,929, a deflectedlaser'li'ght beam is used in conjunction with a holographic characterstorage medium to generate character shapes which are to be directedupon a recording medium.

Such prior art printing apparatus of the general type referred to abovehas not been'fully satisfactory in providing rapidnon-impact printout inalphanumeric'characters of computer data. While gains'have been madeinspeed by eliminating impact, a large disparity from the speed ofthecomputer output-persists. Moreover, many of the prior art devicesemploy elements such as scanners or deflectors which limit speed andrequire a large amount of space, and record data either a characterat atime or a scan line at a time in sequential fashion, often requiringvery rapid switching, a laser light source with a high duty cycle, or aconsiderable amount of activation time per unit of data recorded.

SUMMARY OF THE INVENTION It is a principal object of this invention toprovide an improved high speed, non-impact printer of computer data. Itis a specific object of the invention to provide a printer in which acomplete row of characters may be simultaneously formed, and in whichall character formation may be controlled by electrical or electronicmeans without mechanical devices. Still another object of the inventionis to provide ahigh speed, non-impact printer which is compact, simplein design, and more suitable for commercial use.

In a preferred embodiment of the invention to be described hereinbelowin detail, the printer comprises a row of character printing elements,each with a twodimensional matrix of parallel diode lasers arranged toemit light upon a photosensitive medium continuously transported throughthe system at high speed. Electron ically coded signals for a completerow of characters 'are supplied simultaneously to the printing elementsby, e.g., a computer. Within each printing element the coded signals fora single character are decoded into alphanumeric character signals whichare supplied to a character image generator. The character imagegenerator produces a pattern of on and off signals which drive selecteddiode lasers in the two-dimensional matrix to cause those lasers to emitparallel beams of light in a pattern approximating the shape of thecharacter. The light beams emitted by the row of printing elementssimultaneously strike the photosensitive medium, causing it to recordthe shapes of the characters 'in'the row. This arrangement affords rapidprinting of successive rows of characters. The arrangement further isadvantageous in that is is compact and without the problems introducedby mechanical constituents.

Other objects, aspects and advantages of the invention will be pointedout in, or apparent from, the detailed description hereinbelow,considered together with the following drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of a portion of aprinting apparatus used for recording data on a photosensitivemediiiin'inaccordance with the present'invention;

FIGS. 1A 10 are illustrations of recorded character shapes produced bythe printing apparatus of FIG. 1 on a photosensitive medium, usingvarious laser output unit configurations;

printer which utilizes the laser printing section shown in FIG. 5.

DESCRIPTION or THE PREFERRED EMBODIMENTS The present invention providesa printing apparatus arranged to receive character data in electronicform from a computer and, in response to such data, to print successiverows of visible characters a row at a time on a moving sheet ofphotosensitive recording medium.

'For simplicity a single printing element P, printing a single characterin the row, is illustrated schematically in FIG. 1. As shown, printingelement P receives character data 2 in electronic form from computer 1and prints a single character in the row on photosensitiverecordingmedium 15. The photosensitive recording medium 15 is mounted onrollers 14 for rapid continuous transport through a printing station Swhere printing element P imprints a character by means of short durationlight signals or beams 12 emitter from its laser output unit 10 spacedfrom photosensitive medium 15. Laser output unit 10 contains componentlasens 11 in a two dimensional laser matrix or array, which is typicallya X 7 rectangular array comprising 35 lasers.

Selected lasers in the array emit parallel beams of light 12 in apattern approximating the shape of the character. The emitted lightbeams 12 directly strike the photosensitive medium 15, causing it torecord the character shape, shown typically by the character shape 17 inFIG. 1A, illustrated by the character C'.

Laser output consists of a multi-planar grid or network of parallelsemiconductor lasers in which planar rows of parallel lasers are stackedupon one another. The semiconductor lasers 11 are of a type suitable forrecording images on a photosensitive medium at high speeds. At present,suitable lasers for the application include the single heterojunction(SH), double heterojunction (DH) and large optical cavity (LOC)semiconductor lasers. All three types of lasers have the advantage ofbeing able to operate at very rapid pulsing rates (e.g., less than 10nanoseconds) at comparatively heavy duty cycles for reasonably longlifespans. They can withstand vibration and operate continuously at roomtemperature with only moderate heat-sinking requirements.

Of the three types of presently-suitable lasers, the gallium aluminumarsenide LOC injection laser is preferred. As a refinement of the DHlaser, the LOC laser possesses the high quantum efficiency and lowthreshold current density and heat-sinking requirements of the DH laser,and it is substantially less susceptible to damage by pulsing variationsthan the DH laser. LOC lasers of the type described may be e.g. the RCAC30025 LOC laser, which can be driven by currents as low as 5 amperes ator above room temperature.

Selective activation of the individual lasers 11 in output unit 10(shown greatly enlarged) is accomplished as follows: A source ofelectronic output signals, such as computer 1, transmit anelectronically coded signal representing a numeric, alphanumeric orspecial character of information, such as binary-coded signal 2, tointerface 3. Interface 3 decodes the signal, and applies the decodedsignal to a character image generator 48 comprising a charactertranslator 4, character sense wires 6, pulser 7, and pulser wires 9. Thedecoded signal from interface 3 instructs character translator 4 toactivate the particular one of storage elements 5 which corresponds tothe number, letter or symbol represented by the decoded signal. Thestorage element so activated transmit a unique pattern of electricalimpulses through character sense wires 6 in parallel circuit.

Character sense wires 6 connect with pulser 7 which contains separatedriving circuits or modules 8 for each of the semiconductor lasers 11and serves to convert the presence of current in any character sensewire which contains current to an amplified pulse sufficient to drivethe associated one of the semiconductor lasers 11 in output unit 10.Each one of character sense wires 6 is connected to one of the identicalpulser modules 8 which are equal in number to the number ofsemiconductor lasers 1] in output unit 10. A pulser module 8 switchesthe low-current signals from the character sense wires 6 in a circuitcomprising, for example, a class C operation mode RF transistoramplifier in a pulsed mode of operation. The resulting pulses, typically 40 nanoseconds wide, are transmitted to output unit 10 by means ofpulser wires 9, which would normally be low-inductance ribbon leads.

A one-to-one correspondence exists between each one of pulser modules 8,one of pulser wires 9, and one of semiconductor lasers 1]. The uniquepattern of electrical impulses produced in character sense wires 6 bythe activated one of storage elements 5 is such that the presence oflow-level current is introduced in those of character sense wires 6which are connected to those of pulser modules 8 which serve to drivelasers whose position in the network of semiconductor lasers 1]physically resemble a graphic outline of the number, letter or symbolcorresponding to the storage element activated.

Thus a two dimensional pattern of electric pulses is transmitted inparallel circuit via pulser wires 9 directly to corresponding lasers 11in output unit 10, causing a selective and simultaneous activation ofthose lasers in the array needed to form a composite character beam 13in the shape of the number, letter or symbol corresponding to thestorage element activated. Due to the fact that character-shaped laserbeam 13 is a composite of many smaller, parallel beams, it is initiallyemitted by the apparatus in its final form, and may directly strikephotosensitive recording medium 15 to record an image thereon.

Photosensitive recording medium 15 may typically be embodied as a 14 by11 inch continuous fanfold sheet, chemically treated with aphotopolymer, photoconductor, or photochromic compound sensitive toinfrared light at a wavelength ofapproximately 9000 angstrom units witha minimum radiant flux density of 20.83 watts/mil? For tractor-fedtransport, this continuous sheet would normally have a 16 to 20 poundbond weight, and would be supplied at its peripheries with typicaltractor feeding holes.

Transport rollers 14, typically tractor feeds, impart to photosensitivemedium 15 a continuous, rapid vertical motion. The rate of this verticalmotion may be associated with the pulse width of character-shaped laserbeam 13 to product various types of recorded images, as discussedhereinbelow. Upon striking photosensitive recording medium 15, theparallel beams of light 12 forming character-shaped laser beam 13 causeindividual recordings 16, shown greatly enlarged in FIG. 1A, to be madein an overall graphic shape 17 approximating that of the desiredcharacter. Due to the fact that only one set of electrical impulses istransmitted by the storage element activated, the selected lasersdeactivate immediately following the laser emission of character-shapedbeam 13, leaving output unit 10 ready to accept a new set of electricalimpulses for the next character to be printed at the character portionof unit 10 in the-succeeding row of characters. Between successiveactivations of lasers 11, the transport rollers 14 continue to advancephotosensitive recording medium 15 so that it will be positioned toreceive the next row of character beams 13 emitted.

As illustrated in FIGS. 1B, 1C, 1D and 1E, one of four types of outputunit configurations 10W, 10X, l0Y or 102 may be employed by the printingapparatus P to obtain different types of character shapes 17W or 17Y onphotosensitive recording medium 15. Each output configuration employslenses to rectify the divergenceangle which occurs in presentstate-of-the-art semiconductor lasers. FIGS. 1B and 1C show shortemission time versions of the output unit 10W and 10X which employnarrow laser pulse widths (typically less than 40 nanoseconds). In FIG.18, individual lenses 19W are fitted over the emitting junctions 18W ofthe lasers in a manner well known in the art. The lenses 19W, having alarge numerical aperture, serve to focus the light emitted from lasingjunctions 18W, producing the narrow lines comprising character shape17W. In FIG. 1C, one large collecting lens 20X is used to focus thelight emitted from all of the lasing junctions 18X, producing a similarcharacter shape 17X. However, not all of the divergence angle must berectified by the lenses; in fact, beam divergence serves to spread orenlarge the individual image recordings formed by the parallel laserbeam as they strike the photosensitive medium, yielding a morecontinuous and intelligible character shape of the type illustrated inFIG. 1F.

Shown in FIGS. 1D and 1E are the character shapes l7Y and l7Z producedby a modification of the invention which utilizes extended laser pulsewidths. In this version of the invention, the semiconductor lasers inoutput unit 10Y or 10Z are arranged with their laseremitting junctionsl8Y and 182 perpendicular to the vertical direction of motion ofphotosensitive medium 15. For any given speed of vertical motion ofphotosensitive medium 15, the laser pulse duration used to produce thistype of character shape is normally 5 to 8 times greater than the shortemission pulse used to produce the type of character shape 17W or 17Xshown in FIGS. 18 and 1C. During this extended pulse, photosensitivemedium will have a maximum vertical motion equal to the distance Q shownin FIGS. 1D and 1E, causing the perpendicular active regions 18Y or 18Zto record broad, flat vertical strokes on the moving medium with theirlaser beams. In FIG. 1D and 1E the output units NY and 10Z employindividual lenses 19Y and a large collecting lens 202 in the mannerpreviously described. If a small precentage of divergence were allowedto occur in these cases, an extended character shape of the typeillustrated in FIG. 10 would be produced.

The extended pulse width to produce character shapes l7Y and l7Z isdetermined by the following formula: Where:

T Total time allotted to print a horizontal row of characters V Verticalspacing per line of characters (normally I/6 inch) PW Pulse width QHeight of the array/Vertical number of lasers X a tolerance factor,typically 90-95 percent For an output unit l0Y or 102 0.1 inch highcomprised of 7 horizontal rows of lasers (i.e. seven vertical lasers),using a tolerance factor or 95 percent, 0 has a value of 0.0135 inch.For printing 6 characters to the vertical inch, V would have a value of0.1666 inch. Calculation with these factors shows that the duty cyclerequired for the lasers at any printing speed is solely a function ofthe percent of vertical extension of recordings along the distance 0which may be selected. Major values are summarized in the followingtable:

Percent of Vertical Extension Laser Duty Cycle Percent 12.3 1.0 2s 2.02s50 4.050 75 6.075 100 (full 0) 8.1

Thus for the LOC lasers mentioned, which currently have a 1 percent dutycycle, a vertical recording extension of slightly over 12 percent of thedistance Q shown in FIG. ID and FIG. 1E may be obtained. Numerousmodifications of the apparatus may bedevised to increase thispercentage. For example, the LOC lasers may be cryogenically cooled to77 K to obtain a 4 percent duty cycle. The height of the array may bereduced or the vertical number of lasers may be increased.

For any given duty cycle, the pulse width employed I to obtain thecorresponding percentage of recording distance 0 shown in the abovetable varies inversely with the speed of vertical motion ofphotosensitive medium 15. The speed of vertical motion is directlyproportional to the number of character-shaped laser beams emitted perminute by the output unit IOY or 102. This relationship can also be saidto occur in the short emission time version of the output unit (FIGS. 18and 1C), in that the limit of the maximum pulse width employed by thisversion varies inversely with printing speed. The environment in whichoutput units 10W, 10X, l0Y or 10Z will operate may require fixed orvariable printing speeds. In applications where sustained periods ofoperation are required at constant speeds, the pulse width may be fixedas a constant. In applications requiring operation at varying printingspeeds, or applications requiring frequent start-up and shut-down, thepulse width may be synchronized with printing speed. However it shouldbe mentioned that sustained periods of operation at top-rated speeds arethe expected and most productive environment for the apparatus.

Where clarity of character shapes is the primary concern, the extendedcharacter shapes l7Y and 172 shown in FIGS. 1D and 1E are preferred.However, the largest recorded area per character is provided by thecharacter shape shown in FIG. 16, in which the output unit IOY or 10Zmakes use of a small portion of the divergence angle. Theintelligibility of this character shape is also high. The shorter pulsewidths used in short emission time printing can provide a substantiallylighter duty cycle for the lasers, which may be retained or traded offfor higher printing speeds. For recognition purposes, the short emissiontime character shape shown in FIG. 1F (with a portion of the divergenceangle) is preferred. A similar trade off may be made in the extendedpulsing versions of the output unit 10Y or 102, in which a portion ofthe extended recording area along the distance 0 is traded off for areduced pulse width, allowing for a lighter duty cycle or a higherprinting speed. The arrangement of the laser-emitting junctions l8Y or182 in a perpendicular orientation to the vertical direction of motionof photosensitive medium 15 gives these versions of the output unit 10Yand 102 the greatest degree of flexibility. At present, it is preferableto use the extended pulsing versions of the output unit using eitherlens arrangement (FIG. 1D or IE) to fully rectify the divergence angle,because these versions afford the greatest flexibility, and because thevertically-extended character shapes l7Y and 172, which may be producedonly by these versions, have the highest optical character recognitionquality.

FIG. 2 shows in greater detail one particular embodiment of the elements4 through 6 shown schematically in FIG. 1. In this embodiment, thecharacter translator 4 has its storage elements 5 each formed by anindependent group of character wires 27A, 27B, 27C 27N, whereN is thenumber of unique characters to be formed by the apparatus, and N l isthe number of unique electronically-coded signals which may be receivedby the apparatus (one signal representing a blank or space character).The value of N 1 would normally be 48 or 64, depending upon the numberof special symbols provided for in the character font of the apparatus.Assigning the preferred value of 64 to N 1 would yield 63 separategroups of character wires 27A27N i.e., one group of character wires foreach character in the printable font except for the space character.

When computer 1 transmits to interface unit 3 an electronically-codedsignal representing a printable character, such as binary coded signal2, interface unit 3 decodes the electronic signal and supplies a signalto one particular address sense wire 21A, 21B, 21C 2lN l assigned to thedecoded character and arranged to cause current to be introduced intothe group of character wires 27A27N corresponding to the decodedprintable character. The signal in the one address sense wire 21A-21N soisolated by the interface 3 closes a corresponding address sense switch22A, 22B, 22C 22N, which may typically be a transistor relay. A voltagesource such as transformer 23 is connected by transformer wire 24 toeach of the address sense switches 22A-22N to complete a circuit throughwhichever address sense switch is closed. Voltage from the transformerhaving a value equal to k,. is applied to the selected group ofcharacterwires 27A 27N. The

- value of k,. is selected to meet the voltage requirement of pulser 7for converting a signal in one character wire to an amplifier pulsesufficient to drive a semiconductor laser of the type used in the outputunit. For typical pulsers, the input signal voltage requirement isvalued at approximately 2 volts and is applied through the groups ofcharacter wires 27A27N in parallel. As transformer 23 is connectedthrough whichever address sense switch 22A-22N is closed, it activates acorresponding timing circuit 25A, 25B, 25C 25N, such as an RC circuit,which is connected to reopen the closed address sense switch after apredetermined interval of time. In amplifier type pulsers where thepulse width is determined by the input signal, this interval of timewould normally be equal to the rise time of the pulser, eg 6nanoseconds, plus the width of the pulse desired, e.g. 40 nanoseconds,and thus is typically 46 nanoseconds. ln latching type pulsers where afixed pulse width is triggered by the input signal, this interval oftime is equal to the rise time of the pulser plus a buffer, normally 6plus 12 nanoseconds. Thus the address sense switches 22A, 22B, 22N areregulated to direct a short activating input signal pulse throughaddress resistors 26A, 26B, 26N connected in series between transformer23 and the groups of character wires 27A 27N. The address resistors 26A26N, which have a value related to the source resistance of transformer23 and to the resistances of the pulser modules 8, are used to establishthe appropriate level of input signal current for the pulser modules 8in each of the individual character wires 28 in a group.

Current through an address resistor 26A-26N is applied to thecorresponding group of character wires 27A, 27B, 27C, 27D 27N. Thesegroups of character wires could typically be etched on a printed circuitboard or boards in a manner well known in the art, or could be containedin one or more LSI chips. Each group of character wires is comprised ofa number of individual character wires 28. Forming parallel circuits,these individual character wires 28 carry an actuating current,typically about 4 milliamperes, to individual pulser modules 8. Becausea one-to-one correspondence exists between each of the individualcharacter wires 28 in a group of character wires 27A27N and asemiconductor laser 11 in output unit 10 needed to form a character, itcan be seen that large variations will occur in the numbers ofindividual character wires 28 in the various groups of character wires27A27N. For example, the group of character wires corresponding to theletter W would contain almost four times the number of individualcharacter wires 28 in the group forming the number 1. In order for eachof the individual character wires 28 used in the formation of W tocontain the same amount of current as each of the individual characterwires 28 used in he formation of l, the total amperage in the group ofcharacter wires 27A27N corresponding to W must be almost four times asgreat as the total amperage in the group of character wirescorresponding to 1. Therefore the resistance of the address resistor26A, 26B, etc. used for the W group of character wires is selected tocarry almost four times the current as that of the address resistor usedfor the 1 group of character wires.

Accordingly, character translator 4 supplies a signal of predeterminedlength through each of the individual character wires 28 in the group27A27N to pulser 7 for the duration of its activation and rise orpulsing time at the voltage and amperage it requires to produce onepulse.

The method of character-image generation provided by the embodiment ofFIG. 2 is as follows: All groups of character wires 27A27N converge uponpulser 7 in such a way that the pulser modules 8 to which the individualcharacter wires 28 in each group are connected serve to activate viapulser wires 9 those of semiconductor lasers 11 in output unit 10 whosepositions in the two dimensional laser array physically resemble agraphic outline of the number, letter or symbol corresponding to thegroup of character wires, This concept is illustrated in FIG. 2 bycircles 29, which highlight those of pulser modules 8 to whichindividual character wires 28 from the group of character wires 27C areconnected, and by asterisks 29A, which indicate those of semiconductorlasers 11 in the laser array activated by those of pulser modules 8highlighted by circles 29.

Circles 29 and asterisks 29A form the shape of a C" in the drawing. Thegroup of character wires 27C corresponds to the character C in thisillustration; which is to say that given a binary coded electronicsignal 2 of 1100 0011 (which represents C" in EBCDIC), in-, terface 3will isolate the current of the signal into address sense wire 21C whichwill direct a signal from transformer 23 through address sense switch22C for a period of time determined by timing circuit 25C.

Each wire in the group of character wires 27C carries the resultingactivation current in parallel circuit to pulser 7 where, by means ofthe selected ones of pulser modules 8 to which the individual characterwires 28 in group 27C are affixed, the one dimensional impulse group ofactivation currents is transformed into a two dimensional characteroutline of amplified laser-drive pulses. The semiconductor lasers 11upon which this two dimensional character outline of amplified pulses issuperimposed by means of pulser wires 9 are highlighted by asterisks 29Ain H6. 2.

Through a wiring consolidation which may be achieved by a printedcircuit board, all groups of character wires 27A-27N converge uponpulser 7, and almost every one of pulser modules 8 serve to consolidatethe circuit paths of individual character wires 28 from several groupsof character wires 27A-27N into a common laser pulse sourcecorresponding to one point in the graphic array of the network of lasers11.

Though each of the pulser modules 8 in pulser 7 serves one or most oftena plurality of individual character wires 28 from various groups27A-27N, only some of the pulser modules 8 may be activated at any giventime. This is due to the fact that interface 3 causes electric currentto be introduced into only one group of character wires 27A-27N at anyone time, and no group of character wires 27A-27N uses all of thesemiconductor lasers 11 in output unit 10. Thus in each case ofcharacter emission, the component lasers 1] in output unit 10 areselectively energized. 1n the case of emission of the character C, thepattern of presence and absence of drive pulses in pulser wires 9 issuch that the positions of the component lasers in output unit 11 whichare activated by this pattern of drive pulses will physically resemble aC. For any character in the font of the apparatus, a correspondingcharactershaped laser beam 13 will be formed by output unit 10 in themanner described. Reception of this charactershaped beam 13 byphotosensitive recording medium 15 will cause character-image 17 to beformed on recording medium 13. Absence of further electric current inthe individual character wires 28'causes the selectively-activatedlasers 11 in output unit 10 to deactivate, leaving output unit 10 readyto accept a new pattern of signals for the next character to be printed.

For engineering purposes it is likely that pulser 7, utilizing presentstate-of-the-art hardware, would have the shape of an elongated, thinprinted circuit board; the end of which terminating in pulser wires 9would be adjacent to laser output unit 10. The shape of pulser 7 isshown in the illustrations as spatially coherent with that of outputunit 10 for the purpose of clarity. Referring to FIG. 3, anotherembodiment of the invention is illustrated in which the charactertranslator 4 has storage elements 5 in the form of a read-only corememory. Core stack 30 is comprised of core planes 31A, 31B, 31X, where Xis the number of semiconductor lasers 1] in output unit 10. Core planes31A 31X are constructed so that the number of cores 32 in each plane 31A31X is equal to the number of unique characters to be formed by theapparatus. Assigning the preferred value of 64 characters to theprintable font of the apparatus would yield 64 characters in combinationwith the 5 X 7 matrix of lasers 11 as illustrated would yield a corememory comprised of 35 planes of 64 cores each. As will be apparent tothose skilled in the art, this method of memory construction is ineffect simply defining one register for each character in the font suchthat each register has one bit for each laser in the output unit. Thecondition of each bit (l or 0) will determine the condition of acorresponding laser (on or off) in the manner described hereinbelow.

A source of electronic output signals, such as computer l, transmits anelectronically-coded signal representing a printable character, such asbinary-coded signal 2, to interface 3. lnterface unit 3 decodes theelectronic signal by isolating its current into the corresponding one ofaddress sense wires 2lA-21N, where N represents the number of charactersin the font of the apparatus; e.g. 64. Given a binary-coded signal 2 of1100 0011 (representing C in EBCDlC), interface 3 will isolate thesignal current into the address sense wires 21C shown in thisillustration. Current in the address sense wire 21C will cause anon-destructive read out of the contents of the cores 32 which are shownto be contained in C register 33. In this way, the contents of theselected register, in this case the C register, are transferred to thesense wires 34A, 34B, 34C 34X in the form of the presence or absence ofelectrical impulses. As FIG. 3 shows in detail, the sense wires 34A-34Xare connected to pulser 7 in a predetermined, sequential pattern. Allcores 32 in core plane 31A affect only pulser module 8A in pulser 7 viasense wires 34A. All cores 32 in core plane 31B affect only pulsermodule 8B in pulser 7 via sense wire 34B, and so forth for all theplanes 31A-31X in the stack 30.

The reading of a core 32 in a binary condition of 1 will cause amagnetic induction of electric current into the sense wire 34A34Xserving the plane 31A-31X which contains the core. Because the sensewires 34A-34X are connected to the pulser modules 8 in pulser 7 in thelogical manner described, the method of character-image generationprovided by the embodiment of FIG. 3 emerges as follows: For each of the64 registers in the memory, a binary number can be divised and storedwhich, when read into the sense wires 34A-34X, will cause the presenceand absence of current to be introduced to pulser 7 in such a way thatthe presence of electric current is introduced into those of pulsermodules 8 which serve to activate those of semiconductor lasers 11 inoutput unit 10 whose locations in the two dimensional laser arrayphysically resemble a graphic outline of the number, letter or symbolcorresponding to the register. This concept is illustrated in detail forthe letter C. Cores 32 from C register 33 are shown along with theircorresponding binary values. Those cones 32 having a value of 1 locatedin planes 31A-31X served by sense wires 34A-34X terminating in pulsermodules 8, as indicated by circles 29, will activate those ofsemiconductor lasers 11 whose positions in output unit 10 physicallybelong to the graphic shape of the letter C. All other cores in theregister have a binary value of 0. Thus when the C register is read, thesense wires will carry the presence of electric current induced by thereading of the 1 cores to those pulser modules highlighted by circles29. Being solely a function of the binary number stored in a register,this process of forming a two dimensional character-image comprised ofelectrical pulses in the same for all registers in the memory.

The initial pulsing of low-level current which was accomplished in FIG.2 for signals in the address sense wires 21A-21N by the address senseswitches 22A-22N and timing circuits 25A25N is accomplished in thisembodiment for the core impulses from the sense wires 34A-34X by asimilarly-constructed pre-pulsing section in each of pulser modules 8.The resulting low-current pulse is then converted in the normal way intoa pulse of sufficient magnitude and desired width to drive asemiconductor laser. When this process occurs following the reading of astorage register, the resulting amplified pattern of pulses issuperimposed upon the network of lasers 11 in output unit causingselective activation of those lasers in the array needed to form thecharactershaped laser beam. Reception of this character-shaped beam 13by suitable recording medium 15 will cause character-image 17 to beformed on recording medium 15. Absence of further electric current inthe sense wires 34A-34X causes the selectively-activated lasers 11 inoutput unit 10 to deactivate, leaving output unit 10 ready to accept anew pattern of impulses for the next character to be printed.

In the construction of a high speed laser printing apparatus arranged toprint a row of characters simultaneously and employing a plurality ofthe individual character printing elements P illustrated in FIG. 1, itbecomes advantageous for two or more units of the apparatus whichreceive electronically coded signals at one point in time to emit thecorresponding charactershaped laser beams at the same time, regardlessof which character signals were received. This requires that interfaceunit 3, whose circuitry comprises typically 64 unique signal paths, usethe same amount of time in completing each different path. Owing to thefact that the interface paths used in the decoding of some charactersignals will require more branch decisions than the paths used indecoding other character signals, interface 3 preferably is arranged asshown schematically in FIG. 4 to standardize the interval of timerequired by interface 3 to decode any electronically-coded signal 2 itreceives. Specifically, a circuit is shown in FIG. 4 whereby the currentin two dissimilar signal paths in the interface circuitry undergoes thesame number of switchings to selected paths of logical decision units inthe interface before being isolated as a signal in an address sense wiresuch as 21Y or 212. Source lead 35, which will be assumed to containcurrent, and test lead 36, which may or may not contain current,depending on whether a corresponding bit of signal 2 is a l or a 0,converge upon circuit switch 37. Circuit switch 37, typically ahigh-speed transistor relay, operates such that the absence of currentin test lead 36 will allow the current in source lead 35 to flow throughnormal path 38, and that the presence of current in test lead 36 willcause the current in source lead 35 to be switched or diverted away fromnormal path 38 and channelled into selected path 39. A dummy switch 40,which is identical in construction to circuit switch 37, is insertedinto normal path 38 in the manner shown. Normal path 38 is split intotwo wires above dummy switch 40, so that the presence of current innormal path 38 will act as its own test current, causing dummy switch 40to faithfully divert the normal path current into dummy selected path41. A resistor 42 is provided to prevent by-pass of dummy switch 40.Thus, current in source lead 35 undergoes the same number of switchingsthrough a selected path of a logical decision unit before it is isolatedin terminal 43, for address sense wire 212, or terminal 44, for addresssense wire 21Y. This technique of equalizing the number of switchingsthrough the selected paths of logical decision units is used at everydecision point throughout the interface circuitry. Since some charactersignal paths will contain more of these branch decision points thanother character signal paths, additional dummy switches are added to theshorter character signal paths. The result is that all signal paths inthe interface require the same number of switchings as the numberrequired by the longest signal path in the interface. Equalizing thenumber of these selected switchings required for all signal paths isequivalent to equalizing the amount of time required to interface anysignal. Thus a uniform interface time for all signals is obtained.

Referring to FIG. 5, multiple printing elements P, whose interfaces 3,character image generators 48, and laser output units 10 areindividually depicted in FIG. 1, are shown arranged in a laser printingsection suitable for use in a high-speed, non-impact, on-liner printer.Multiple laser output units 10A, 10B, ION are arranged in a stationary,horizontal row which is parallel to and adjacent to the surface ofphotosensitive recording medium 15 and which extends transversely to thedirection of travel of the recording medium. In this configuration, Nrepresents the number of printing positions in a row of characters to besimultaneously printing in the apparatus. Normally N would have a valueof 132 or 144 printing positions as these are standard in the industry.Assigning the preferred value of 144 to N would yield a stationary,horizontal row of 144 laser output units 10A 10N. As discussedhereinbelow, all of these output units 10A 10N are simultaneouslyactivated so that an entire 144 character line is'printed onphotosensitive recording medium 15. The photosensitive recording medium15 is in continuous vertical motion, which enables it to receiveconsecutive lines of information from the stationary horizontal row oflaser output units 10A 10N at considerable speed.

As shown in FIG. 5, a computer output cable 45 is comprised of I44signal cables 46A, 46B, 46C, 46D 46N which in turn (for an EBCDIC 64character font) are comprised of 8 wires each carrying one bit ofinformation (not shown). Each of the signal cables 46A 46N is connectedto a corresponding one of the interface units 3A, 3B, 3C, 3D 3N by meansof a cable plug 47A, 47B, 47C, 47D 47N. Upon program command to print aline of information, a computer will simultaneously transmit, via signalcables 46A 46N, I44 binary-coded signals which correspond to thecharacters to be printed. (The pattern of presence and absence ofelectric current in the 8 wires comprising each signal cable 46A 46Nrepresents each binary signal, as is well-known in the art.) Thecomputer transmission is simultaneously received by the 144 interfaceunits 34A 3N, which decode the signals with a uniform time delay in themanner previously described with reference to FIG. 4. Character imagegenerators 48A, 48B, 48C, 48D 48N are instructed by their correspondinginterface units 3A 3N to form those patterns of electrical impulseswhich correspond to the characters whose signals were decoded. Transferof these impulse patterns to laser output units 10A 10N causes selectiveactivation of those semiconductor lasers needed to form correspondingcharacter-shaped laser beams 13A, 13B, 13C, 13D 13N. Reception of thesecharacter-shaped laser beams l3A- 13N by photosensitive recording medium15 results in the formation of character images 17A, 17B, 17C, 17D 17Non photosensitive recording medium 15. Deactivation of the selectedlasers in output units 10A ION occurs in the manner previouslydescribed, leaving the printing section ready to accept a new discreteset of 144 electronically'coded signals corresponding to .the next rowof characters to be printed.

Turning now to the overall aspects of the printing apparatus it can beseen that the elements 3, 48 and 10, forming printing elements P forindividual characters, are arranged in rows, indexed by the letters A,B, C, D N. The printing elements P are ideally suited to function in theprinting apparatus because of their ability to be synchronized. Asdepicted in FIG. 4, interface units 3A-3N may be constructed in such away that the time necessary to decode an electronic output signalreceived is a constant for any signal. Character-image generators48A-48N may utilize a hard'wiring scheme as shown in FIG. 2. Given thatthe address sense switches 22A-22N shown in FIG. 2 are of identicalconstruction, and given that the time required by the pulser to generatein parallel any pattern of electric pulses may be considered asconstant, it will be apparent that the apparatus illustrated in FIG. 2requires the same amount of time to generate any character-image.Character-image generators 48A-48N may alternatively utilize a corememory scheme as shown in FIG. 3. It will be apparent that the sameamount of time is required to read any register in a core memory of thesize illustrated. Thus, whether a hard-wiring or core storage scheme isused for character-image generators 48A-48N, the generation of each ofthe 64 characterimages provided for will require the same amount oftime. Referring to the laser output units lA-l0N it can be appreciatedthat the amount of time necessary to activate any number ofsemiconductor lasers in parallel circuit is a constant. Due to the factthe the semiconductor lasers in each output unit l0A-l0N are in aparallel circuit, the length of time required for the selective laserformation of any character in the 64 character font is a constant. Thusthe reception-emission time T defined as the interval of time startingwith the reception of one electronically-coded signal via one of thesignal cables 46A-46N and ending with the emission of one of thecorresponding character-shaped laser beams l3A-l3N, emerges as aconstant for any decodable signal received by a printing element, and ifall electronically coded signals for a row are received simultaneously,all characters in a row will be printed simultaneously.

The interval of time T typically involves a l nanosecond activation time(rise time of radiant flux) for the LOC injection lasers mentioned, a6nanosecond pulser rise time and a uniform interface time of 90nanoseconds, and thus a 100 nanosecond receptionemission time is typicalfor a printing element employing a hard-wired character-image generator.For a printing element employing a core memory characterimage generator,the reception-emission time would be somewhat longer.

In FIG. it can be seen that each group of the components 3, 48 and 10forming a printing element P is identical in each of the rows A, B, C,D, N; in other words, all of the 144 printing elements are identical.This uniformity of elements greatly enhances the ease of manufacturingthe laser printing apparatus, as well as the ease of servicing itscomponents. The interchangeability of the printing elements in theprinting section is important also because it allows for a higherorderlevel of synchronization in the device. Since all elements areidentical, it follows that all printing elements have the samereception-emission time T for any character in the printable font, andsimultaneous reception of electronically coded signals means that allcharacters in a row are formed simultaneously.

Thus 144 printing elements which each receive one of a discrete set of144 electronically-coded output signals at the same instant in timewill, following the reception-emission time interval T simultaneouslyemit the 144 character-shaped laser beams which correspond to theelectronic signals received. Due to the fact that the printing sectioncan simultaneously receive yet independently process all of the signalsin a discrete set of electronically coded output signals, the entireprinting section illustrated operates within one reception-emission timeinterval T for each discrete set of electronically coded output signalsit receives. The operating time for the entire printing section thus isequivalent to the T for any one of the composite printing elements.Given the simultaneous reception of 144 electronically-coded outputsignals by a laser printing section having an overall operating timeequal to the T of each ofits composite printing elements, it followsthat the interval of time starting with the earliest laser-emission of acharacter-shaped beam and ending with the latest laser-emission of acharacter-shaped beam would be zero; i.e., the entire 144 characterlightimage line of print would be emitted at one exact instant in time.

Theoretically, printing can occur at a number of lines per secondlimited only by the duration of T Naturally, this is a theoretical idealwhich is limited not only by the allowance of laser de-activation time,but by the variances, however small, in the printing section circuitrytiming as well as the circuitry timing of the output source computer.However the design of the printing section itself compensates to somedegree for both possible imperfections in its own electronic componentsand for non-simultaneous computer transmis- T,.,= l/M V/lOO where Mrepresents the maximum number of inputs of discrete sets ofelectronically-coded signals per second,

and V represents the greatest allowable percent of vertical positionvariance in the line of characters 17A-17N appearing upon therapidly-moving recording medium 15.

Though it is not uncommon to find electromechanical printouts with ahorizontal variance of as much as 20 percent, the far stricter value of3 percent is normally assigned to V. The formula shows that large timevariances in the printing section components and the reception ofindividual electronically-coded signals in a discrete set of outputsignals can be tolerated by the laser printing section at slow speeds.

For example, at l00,000 lines per minute, the transport mechanism of theprinting device shown in FIG. 6 will produce continuous vertical motionin continuous photosensitive recording medium 15 at the rate of 15.7821miles per hour, in order ot obtain 6 lines of print to the verticalinch. A 3 percent horizontal variance within the vertical 1/6 inchallotted to each line of print would amount to 0.005 inch. At 15.7821miles per hour, this 0.005 inch of continuous photosensitive paper 15would be transported past the stationary, horizontal row of laser outputunits lA-10N in 18 microseconds. lt follows then that in order for theone character image (17A-17N) whose character-shaped laser beam wasemitted last to appear no lower on rapidlymoving photosensitive paperthan 0.005 inch from the one character image (17A17N) whosecharactershaped laser beam was emitted first, the interval of timebetween the first and last laser-emissions of characters in the 144character line must be no longer than 18 microseconds. Thus for V equalto 3 percent, the accumulation of all variances in printing sectioncomponents and signal reception may be tolerated up to and including atotal of 18 microseconds of variance, which therefore is the time T,.,for the printing speed and other conditions mentioned. With a selected Vheld constant, the relationship of T and lines per minute forms a normalhyperbola; for example, T at 350,000 LPM would be 5.14285 microseconds,and at 500,000 LPM T would be 3.60 microseconds for V at 3 percent.Given that all electronically-coded signals in a discrete set of outputsignals corresponding to a line of characters to be printed aretransmitted by the output source computer via parallel circuit in oneoperational cycle, the advantages of higher speeds may be obtainedsimply by insuring that the time variances in the printing sectioncomponents, primarily any operational time variances in the interfacesolid-state relays and any activation time variances in the injectiondiode lasers, are properly controlled and sufficiently refined.

Thus multiple character printing elements P as depicted in FIG. 1 arearranged in a row as a laser printing section, forming a stationary,horizontal row of laser output units 10A-l0N. Each printing elementsimultaneously receives and independently processes one of a discreteset of computer signals which correspond to a line of characters to beprinted. At the end of its operating phase, each printing element emitsa charactershaped laser beam 13A13N which corresponds to the signal itreceived, causing the line of printed characters 17Al7N to be formed ona rapidly-moving recording medium 15. Due to the interchangeability ofthe printing elements, the operating phase of the printing section istheoretically identical to the operating phase of each of the printingelements. The design of the printing section allows it to compensate forrelatively large divergences from this theoretical ideal at slow speeds.Owing to the fact that a full line of characters is printed withoutmoving parts, the primary limit to the highest printing speed attainableby the device is only the maximum duty cycle of the lasers employed, inconjunction with the degree of refinement and control which can beaccomplished in the time variances of its electronic components, and inthe synchronization of the output source computer itself.

Turning now to FIG. 6, a high-speed, non-impact printing apparatusaccording to the invention is depicted. An electronic signal source,such as computer 1, transmits output signals to the printing devicethrough cable 45. These signals are received, translated and processedby printer circuitry 49, which would include the interfaces andcharacter-image generators for each signal. Attached to printercircuitry 49 is a stationary horizontal row of laser output units 50,arranged such that each available printing position along the length ofpinfeed drum 51, carrying a sheet photosensitive recording medium 15,corresponds to a unique output unit in the row. Drive motor 52 rotatesthe pinfeed drum 5] in a clockwise direction, thus accomplishing pinfedtransport of the continuous sheet of photosensitive recording medium 15in a manner well known in the art. Drive motor control 53 includes arheostat to allow manual regulation of the speed of rotation of thepinfed drum 51. Because this speed of rotation may be considerable,retension rollers 54 are employed to insure smooth feeding of thecontinuous sheet of recording medium 15 through the device. The rate atwhich the electronic signal source, such as computer 1, transmits itsoutput signals to the printing device is synchronized with the rotationof pinfeed drum 51 means of a synchronization device 55. The operationof this device is as follows: The circuit connection between lead wire56 and 57 is controlled by a photoelectric switch 58, above which theperimiter of pinfeed drum 51 rotates. Narrow light-admitting slits 59are located in the circumference of penfeed drum 51 such that a 1/6 inchspacing exists between each of the slits. Thus for every 1/6 inchof'rotation of pinfeed drum 5], one of the narrow light-admitting slits59 passes between constant light source 60 and photoelectric switch 58.Light striking photoelectric switch 58 causes it to complete the circuitbetween lead wires 56 and 57. Completion of this circuit indicates tothe electronic signal source, such as computer 1, that the printingdevice is in a receiving status for the next line of output informationto be printed. In this way the printing device is synchronized to print6 lines to the vertical inch at any printing speed which may beselected.

Although specific embodiments of the invention have been disclosedherein in detail, it is to be understood that this is for the purpose ofillustrating the invention, and should not be construed as necessarilylimiting the scope of the invention, since it is apparent that manychanges can be made to the disclosed structures by those skilled in theart to suit particular applications.

The invention claimed is: l. A high-speed non-impact printing apparatusarranged to receive character data in the form of coded electronicsignals and, in response to such data, to print successive rows ofalphanumeric characters on a sheet of photosensitive recording mediumcontinuously transported through the apparatus in a direction transverseto the rows, comprising:

optical output means formed of a two-dimensional matrix of parallelsemiconductor lasers arranged to occupy an area corresponding to a rowof characters to be printed and having a group of lasers for eachcharacter position in the row, said optical output means having for eachlaser an input for receiving a laser activation signal to independentlyactivate the laser, the optical output means being mounted adjacent tobut out of direct contact with the photosensitive recording medium sothat light emitted from activated lasers in the matrix will transmit toand strike the medium and record an image thereon;

.interface means for simultaneously decoding a set of coded electronicsignals corresponding to a row of characters to be printed and forsimultaneously producing, for each character position in the row, anindividual signal'representing the single alphanumeric character to beprinted in that character position; and character-image generating meanshaving inputs for receiving the simultaneous decoded individual signalscorresponding to the row of characters to be printed and having outputsconnected to the inputs of the optical output means, the character-imagegenerating means simultaneously supplying to each group of lasers in theoptical output means a corresponding pattern of laser activation signalsto cause the activated lasers in the group to emit parallel beams oflight in a pattern approximating the shape of the character to beprinted at that position;

said character image generating means having, for each characterposition in the row, storage means for associating each separate decodedindividual signal with a corresponding pattern of laser activationsignals at the outputs to approximate the shape of the correspondingcharacter, and means for generating said patterns of laser activationsignals in response to said decoded individual signals;

means for transporting the photosensitive recording medium through theprinting apparatus;

means for applying the set of coded electronic signals tothe interfacemeans; and

means for coordinating the recording medium transporting means with theelectronic signal applying means to provide uniform spacing betweensuccessive rows of characters printed on the recording medium despitevariations in relative speed of presentation for printing of therecording medium and coded electronic signals, said coordinating meansincluding means for providing a timing signal corresponding to theavailability for printing of a row of coded character signals and a rowof recording medium, and means responsive to the timing signal forsynchronizing the application of the character signals with thetransport of the recording medium to provide even spacing between rowsof printed characters;

whereby said printing apparatus simultaneously imprints a complete rowof character shapes upon said photosensitive recording medium, andwhereby spacing between successive rows of characters on the recordingmedium will be uniform.

2. A high speed non-impact printing apparatus as claimed in claim 1wherein the interface means for simultaneously decoding a set of codedelectronic signals comprises logical decision units receiving said codedsignals and performing switching operations to complete a path to anoutput terminal to provide one of said individual signals in accordancewith the coded information, said decision units being arranged so thateach path therethrou'gh to a separate output terminal representing anindividual signal contains the same number of switching operations,whereby the switching delay is equalized for each separate individualsignal, and the separate individual signals for all the characters inthe row are simultaneously produced.

3. A high speed non-impact printing apparatus as claimed in claim 1wherein, in said character-image generating means, the storage meansassociating each separate decoded individual signal with a correspondingpattern of laser activation signals at said output comprises independentgroups of character wires connected to complete a circuit in common tothe corresponding patterns of outputs, and wherein the means forgenerating said pattern of laser activation signals comprises means forapplying a signal to a selected group of character wires. v

4. A high speed non-impact printing apparatus as claimed in claim 3wherein said character image generating means comprises pulsing meansfor each of said lasers, and wherein the means applying a signal in eachof said character wires applys a predetermined signal necessary toactivate said pulsing means.

5. A high-speed non-impact printing apparatus as claimed in claim 1wherein, in said character image generating means, the storage means forassociating each separate decoded individual signal with a correspondingpattern of laser activation signals at said outputs comprises a corememory with a plurality of registers corresponding in number to thenumber of sepa rate decoded individual signals, each register having anumber of storage elements corresponding to the number of lasers in eachgroup of lasers for a character position, said storage elements beingconnected to said outputs and being set to provide the correspondingpattern of laser activation signals at the output upon reading of eachstorage register.

6. A high speed non-impact printing apparatus as claimed in claim 1wherein the means for transporting said photosensitive recording mediumto the printing apparatus comprises a drum rotating at a speedproportional to the speed of the recording medium, and the meansproviding a timing signal includes means associated with said drum forproviding a timing signal corresponding to the advance of said recordingmedium by a predetermined distance selected to be the spacing betweensuccessive rows of characters on the recording medium, and the meansresponsive to the timing signal includes means for applying the set ofcoded electronic signals to the interface means in synchronization withthe timing signal, whereby spacing between successive rows of characterson the recording medium will be uniform despite variations in speed ofthe recording medium through the printing apparatus.

7. A high speed non-impact printing apparatus as claimed in claim 6wherein the means for generating a timing signal comprises a maskrotating with said drum and photosensitive means detecting apertures insaid mask.

8. A high speed non-impact printing apparatus as claimed in claim 1wherein said character image generating means is arranged to supplylaser activation signals having a duration correlated with the speed ofthe photosensitve recording medium through the apparatus to cause theimages recorded on the photosensitive medium to be extended into thespaces between adjacent lasers in the matrix. 7

9. A high speed non-impact printing element arranged to receivecharacter data in the form of coded electronic signals and, in responseto such data, to print successive alphanumeric characters on a sheet ofphotosensitive recording medium continuously transported by the printingelement, comprising:

optical output means formed of a two dimensional matrix of parallelsemiconductor lasers arranged to occupy an area corresponding to acharacter position to be printed, said optical output means having foreach laser an input for receiving a laser activation signal toindependently activate the laser, the optical output means being mountedadjacent to the photosensitive recording medium so that light emittedfrom activated lasers in the matrix will strike the medium and recordand image thereon;

interface means for simultaneously decoding a set of coded electronicsignals corresponding to the character to be printed and for producing,with a uniform time for each different character, an individual signalrepresenting the single alphanumeric character to be printed in thatcharacter position; and

character-image generating means having inputs for receiving the decodedindividual signals corresponding to the character to be printed andhaving outputs connected to the inputs of the optical output means, thecharacter-image generating means simultaneously supplying to the lasersin the optical output means a corresponding pattern of laser acti vationsignals to cause the activated lasers in the group to emit parallelbeams of light in a pattern approximating the shape of the character tobe printed at that position;

said character-image generating means having storage means forassociating each separate decoded individual signal with a correspondingpattern of laser activation signals at the outputs to approximate theshape of the corresponding character, and means for generating saidpatterns of laser activation signals in response to said decodedindividual signals;

means for transporting the photosensitive recording medium past theprinting element;

means for applying the set of coded electronic signals to the interfacemeans; and

means for coordinating the recording medium trans porting means with theelectronic signal applying means to provide uniform spacing betweensuccessive characters printed on the recording medium despite variationsin relative speed of presentation for printing of the recording mediumin coded electronic signals, said coordinating means including means forproviding a timing signal corresponding to the availability for printingthe coded character signals and an element of recording medium, andmeans responsive to the timing signal for synchronizing the applicationof the coded electronic signals with the transport of the recordingmedium to provide even spacing between printed character elements.

10. A high speed non-impact printing apparatus as claimed in claim 9wherein the interface means for simultaneously decoding a set of codedelectronic signals comprises logical decision units receiving said codedsignals and performing switching operations to complete a path to anoutput terminal to provide one of said individual signals in accordancewith the coded information, said decision units being arranged so thateach path therethrough to a separate outut terminal representing anindividual signal contains the same number of switching operations,whereby the switching delay is equalized for each separate individualsignal.

11. A high speed non-impact printing apparatus as claimed in claim 9wherein, in said character-image generating means, the storage meansassociating each separate decoded individual signal with a corresponding pattern of laser activation signals at said output comprisesindependent groups of character wires connected to complete a circuit incommon to the corresponding patterns of outputs, and wherein the meansfor generating said pattern of laser activation signals comprises meansfor applying a signal to a selected group of character wires.

12. A high speed non-impact printing apparatus as claimed in claim 11wherein said character-image generating means comprises pulsing meansfor each of said lasers, and wherein the means applying a signal in eachof said character wires applies a predetermined signal necessary toactivate said pulsing means.

13. A high speed non-impact printing apparatus as claimed in claim 9wherein, in character image generating means, the storage means forassociating each separate decoded individual signal with a correspondingpattern of laser activation signals at said outputs comprises a corememory with a plurality of registers corresponding in number to thenumber of separate decoded individual signals, each register having anumber of storage elements corresponding to the number of lasers in theoptical output means, said storage elements being connected to saidoutputs and being set to provide the corresponding pattern of laseractivation signals at the output upon reading of each storage register.

14. A high speed non-impact printing apparatus as cent lasers in thematrix.

. i Page 1 of 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONJohn L. Mee

Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patentare hereby corrected as shown below:

In the specification 1 Column 2, line 66, change "emitter" to -emitted-.

.1 Column 2, ,line 68, change lasens" to -lasers-.

Column 3, line 9,- after "output" insert unit. Column 3 line 37, change"transmit" to -transmits-:. Column 3, line 48, change "transmit" totransmits-i. Column 4, line 39, change "product" toproduce.

Column 5, line 12, change "beam" to -beams-. I Column 5, line 20, change"and" to or.

lg Column 5, line 35, change "precentage" to percentage-. I

Column 5, line 40, change "and" to or-.

? Column 5, line 53, change "or" to -of.

Column 7, line 35, change "amplifier" to amplified.

FORM PO-1 (10- uscoMM-oc 60376-P69 Q U.5 GOVERNMENT PRINTING OFFICE l990-856-33L Page 2 of 5 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 5 ,9 7 Dated Sept. 17, 197A Inventor(s) John L.Mee

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 9, line 7, change "serve" to servesm Column 9 line 58, after"yield" insert 64 cores per plane. Thus, for example, a font of-.

Column 10, line 11, change "wires" to wire-.

Column 10, line 22, v change "wires" to -wire.

Column 10, line 45, change "cones" to cores-; change 1" to l'. i

Column vl0, line 51, change "0" to 'O Q 7 Column 12, line 13, change"on-liner" to -online.

Column 12, line 21, change "printing" to printed.

Column 12, line 50, change "34A" to 3A.

Column 13, line 18, change "as" to -a-.

Column 15, line 1, change "ot" to to.

1. A high-speed non-impact printing apparatus arranged to receivecharacter data in the form of coded electronic signals and, in responseto such data, to print successive rows of alphanumeric characters on asheet of photosensitive recording medium continuously transportedthrough the apparatus in a direction transverse to the rows, comprising:optical output means formed of a two-dimensional matrix of parallelsemiconductor lasers arranged to occupy an area corresponding to a rowof characters to be printed and having a group of lasers for eachcharacter position in the row, said optical output means having for eachlaser an input for receiving a laser activation signal to independentlyactivate the laser, the optical output means being mounted adjacent tobut out of direct contact with the photosensitive recording medium sothat light emitted from activated lasers in the matrix will transmit toand strike the medium and record an image thereon; interface means forsimultaneously decoding a set of coded electronic signals correspondingto a row of characters to be printed and for simultaneously producing,for each character position in the row, an individual signalrepresenting the single alphanumeric character to be printed in thatcharacter position; and character-image generating means having inputsfor receiving the simultaneous decoded individual signals correspondingto the row of characters to be printed and having outputs connected tothe inputs of the optical output means, the character-image generatingmeans simultaneously supplying to each group of lasers in the opticaloutput means a corresponding pattern of laser activation signals tocause the activated lasers in the group to emit parallel beams of lightin a pattern approximating the shape of the character to be printed atthat position; said character image generating means having, for eachcharacter position in the row, storage means for associating eachseparate decoded individual signal with a corresponding pattern of laseractivation signals at the outputs to approximate the shape of thecorresponding character, and means for generating said patterns of laseractivation signals in response to said decoded individual signals; meansfor transporting the photosensitive recording medium through theprinting apparatus; means for applying the set of coded electronicsignals to the interface means; and means for coordinating the recordingmedium transporting means with the electronic signal applying means toprovide uniform spacing between successive rows of characters printed onthe recording medium despite variations in relative speed ofpresentation for printing of the recording medium and coded electronicsignals, said coordinating means including means for providing a timingsignal corresponding to the availability for printing of a row of codedcharacter signals and a row of Recording medium, and means responsive tothe timing signal for synchronizing the application of the charactersignals with the transport of the recording medium to provide evenspacing between rows of printed characters; whereby said printingapparatus simultaneously imprints a complete row of character shapesupon said photosensitive recording medium, and whereby spacing betweensuccessive rows of characters on the recording medium will be uniform.2. A high speed non-impact printing apparatus as claimed in claim 1wherein the interface means for simultaneously decoding a set of codedelectronic signals comprises logical decision units receiving said codedsignals and performing switching operations to complete a path to anoutput terminal to provide one of said individual signals in accordancewith the coded information, said decision units being arranged so thateach path therethrough to a separate output terminal representing anindividual signal contains the same number of switching operations,whereby the switching delay is equalized for each separate individualsignal, and the separate individual signals for all the characters inthe row are simultaneously produced.
 3. A high speed non-impact printingapparatus as claimed in claim 1 wherein, in said character-imagegenerating means, the storage means associating each separate decodedindividual signal with a corresponding pattern of laser activationsignals at said output comprises independent groups of character wiresconnected to complete a circuit in common to the corresponding patternsof outputs, and wherein the means for generating said pattern of laseractivation signals comprises means for applying a signal to a selectedgroup of character wires.
 4. A high speed non-impact printing apparatusas claimed in claim 3 wherein said character image generating meanscomprises pulsing means for each of said lasers, and wherein the meansapplying a signal in each of said character wires applys a predeterminedsignal necessary to activate said pulsing means.
 5. A high-speednon-impact printing apparatus as claimed in claim 1 wherein, in saidcharacter image generating means, the storage means for associating eachseparate decoded individual signal with a corresponding pattern of laseractivation signals at said outputs comprises a core memory with aplurality of registers corresponding in number to the number of separatedecoded individual signals, each register having a number of storageelements corresponding to the number of lasers in each group of lasersfor a character position, said storage elements being connected to saidoutputs and being set to provide the corresponding pattern of laseractivation signals at the output upon reading of each storage register.6. A high speed non-impact printing apparatus as claimed in claim 1wherein the means for transporting said photosensitive recording mediumto the printing apparatus comprises a drum rotating at a speedproportional to the speed of the recording medium, and the meansproviding a timing signal includes means associated with said drum forproviding a timing signal corresponding to the advance of said recordingmedium by a predetermined distance selected to be the spacing betweensuccessive rows of characters on the recording medium, and the meansresponsive to the timing signal includes means for applying the set ofcoded electronic signals to the interface means in synchronization withthe timing signal, whereby spacing between successive rows of characterson the recording medium will be uniform despite variations in speed ofthe recording medium through the printing apparatus.
 7. A high speednon-impact printing apparatus as claimed in claim 6 wherein the meansfor generating a timing signal comprises a mask rotating with said drumand photosensitive means detecting apertures in said mask.
 8. A highspeed non-impact printing apparatus as claimed in claim 1 wherein saidcharacter image generating means is arranged to sUpply laser activationsignals having a duration correlated with the speed of the photosensitverecording medium through the apparatus to cause the images recorded onthe photosensitive medium to be extended into the spaces betweenadjacent lasers in the matrix.
 9. A high speed non-impact printingelement arranged to receive character data in the form of codedelectronic signals and, in response to such data, to print successivealphanumeric characters on a sheet of photosensitive recording mediumcontinuously transported by the printing element, comprising: opticaloutput means formed of a two dimensional matrix of parallelsemiconductor lasers arranged to occupy an area corresponding to acharacter position to be printed, said optical output means having foreach laser an input for receiving a laser activation signal toindependently activate the laser, the optical output means being mountedadjacent to the photosensitive recording medium so that light emittedfrom activated lasers in the matrix will strike the medium and recordand image thereon; interface means for simultaneously decoding a set ofcoded electronic signals corresponding to the character to be printedand for producing, with a uniform time for each different character, anindividual signal representing the single alphanumeric character to beprinted in that character position; and character-image generating meanshaving inputs for receiving the decoded individual signals correspondingto the character to be printed and having outputs connected to theinputs of the optical output means, the character-image generating meanssimultaneously supplying to the lasers in the optical output means acorresponding pattern of laser activation signals to cause the activatedlasers in the group to emit parallel beams of light in a patternapproximating the shape of the character to be printed at that position;said character-image generating means having storage means forassociating each separate decoded individual signal with a correspondingpattern of laser activation signals at the outputs to approximate theshape of the corresponding character, and means for generating saidpatterns of laser activation signals in response to said decodedindividual signals; means for transporting the photosensitive recordingmedium past the printing element; means for applying the set of codedelectronic signals to the interface means; and means for coordinatingthe recording medium transporting means with the electronic signalapplying means to provide uniform spacing between successive charactersprinted on the recording medium despite variations in relative speed ofpresentation for printing of the recording medium in coded electronicsignals, said coordinating means including means for providing a timingsignal corresponding to the availability for printing the codedcharacter signals and an element of recording medium, and meansresponsive to the timing signal for synchronizing the application of thecoded electronic signals with the transport of the recording medium toprovide even spacing between printed character elements.
 10. A highspeed non-impact printing apparatus as claimed in claim 9 wherein theinterface means for simultaneously decoding a set of coded electronicsignals comprises logical decision units receiving said coded signalsand performing switching operations to complete a path to an outputterminal to provide one of said individual signals in accordance withthe coded information, said decision units being arranged so that eachpath therethrough to a separate outut terminal representing anindividual signal contains the same number of switching operations,whereby the switching delay is equalized for each separate individualsignal.
 11. A high speed non-impact printing apparatus as claimed inclaim 9 wherein, in said character-image generating means, the storagemeans associating each separate decoded individual signal with acorresponding pattern of laser activatIon signals at said outputcomprises independent groups of character wires connected to complete acircuit in common to the corresponding patterns of outputs, and whereinthe means for generating said pattern of laser activation signalscomprises means for applying a signal to a selected group of characterwires.
 12. A high speed non-impact printing apparatus as claimed inclaim 11 wherein said character-image generating means comprises pulsingmeans for each of said lasers, and wherein the means applying a signalin each of said character wires applies a predetermined signal necessaryto activate said pulsing means.
 13. A high speed non-impact printingapparatus as claimed in claim 9 wherein, in character image generatingmeans, the storage means for associating each separate decodedindividual signal with a corresponding pattern of laser activationsignals at said outputs comprises a core memory with a plurality ofregisters corresponding in number to the number of separate decodedindividual signals, each register having a number of storage elementscorresponding to the number of lasers in the optical output means, saidstorage elements being connected to said outputs and being set toprovide the corresponding pattern of laser activation signals at theoutput upon reading of each storage register.
 14. A high speednon-impact printing apparatus as claimed in claim 9 wherein saidcharacter image generating means is arranged to supply a laseractivation signal having a duration correlated with the speed of thephotosensitive recording medium through the apparatus to cause the imagerecorded on the photosensitive medium to be extended into the spacebetween adjacent lasers in the matrix.